Oberheim_Two-Voice_Service_Manual 电路图.pdf

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1、Oberheim Two-Voice Instruction Manual when the switch is on , voice module two will not be gated until a second key is depressed. 3: The PORTAMENTO control, normally left fully counterclock- wise, introduces a lengthening pitch slide between different notes on the keyboard as it is rotated to the ri

2、ght. 4: The TRANSPOSE control switches the keyboard voltage one volt at a time through a range of three volts, resulting in one- octave transpositions of the two VCOs. 5: The PITCH BEND control, normally centered, bends the key- board voltage up or down as it is rotated, producing a cor- responding

3、pitch bend from the two oscillators. RadioFans.CN 收音机爱 好者资料库 2 The MINI-SEQUENCER is described separately on a following page. So are the VOICE MODULES; the controls of each module are iden- tical to those of the other, the only difference between them being in the way they are controlled by the key

4、board and sequencer modules. The OUTPUT MIXER consists of only three rotary pots and two phone jacks. The Jack connections are shown in the diagram, and the pots are: 6: the OUTPUT LEVEL CONTROL for voice module one, 7: the OUTPUT LEVEL CONTROL for voice module two, and 8: the MASTER OUTPUT CONTROL

5、for the synthesizer. SETTING THE STAGE Before connecting your Oberheim synthesizer to headphones or to an amplifier, be sure that the master output control is fully off (counterclockwise). After making the external connection to headphones or ampli- fier, you may turn the synthesizer on. Locate the

6、ASSIGNMENTS switches in the minisequencer section, and be sure that they are all down . In each voice module, set the controls to the positions shown on the following page by the asterisks; where there is no asterisk use the position in the photograph itself. You may now turn, if you want to, direct

7、ly to the section called FIRST STEPS and begin to explore the synthesizer. But it would probably be better to spend just a few minutes reading through the descriptions of the minisequencer and the voice modules first. On the other hand, it would be a mistake to try to memorize in detail everything i

8、n the descriptions following; they contain some important facts-usually in italics-and some less impor- tant but still useful information. Some of this will become familiar to you simply from habit as you work with the synthe- sizer. 3 THE MINI-SEQUENCER AND SAMPLE/HOLD. 1. The CONTROL VOLTAGE PRESE

9、TS determine two different output voltages at each of the sequencers eight positions. Each num- bered position in this section of the panel has two independent concentric rotary pots. The outside pot controls the SEQUENCE OUTPUT ONE, and the inner pot determines SEQUENCE OUTPUT TWO. An LED at each p

10、osition is illuminated when that position is active. 2. The VOLTAGE ASSIGNMENT SWITCHES determine the source and destination of voltages from the sequencer and sample/hold. In the module illustrated there are four switches. In the module included with the 2-voice synthesizer there are three switches

11、; the description following applies to the three-switch version. The first switch on the left selects the source of control voltages and gates for VOICE MODULE ONE. In its lowest posi- tion, voice module one will be controlled by the keyboard only, and will not be affected by either the sequencer ou

12、tput volt- ages or the sample/hold output voltages. In the center position of this switch, voice module one will be gated by the CLOCK (#5 below) and its VCOs will be controlled by the output of the SAMPLE/HOLD (#4 below). When the switch is in its highest posi- tion, voice module one will be gated

13、by the CLOCK and its VCOs will be controlled by SEQUENCE OUTPUT ONE. The second switch performs the same selecting function for VOICE MODULE TWO, except that in its uppermost position the VCOs in voice module two will be controlled by SEQUENCE OUTPUT TWO rather than sequence output one. 4 The third

14、switch allows either KEYBOARD VOLTAGE ONE or KEYBOARD VOLTAGE TWO to be added, respectively, to either SEQUENCE OUT- PUT ONE or SEQUENCER OUTPUT TWO. Thus one of the keyboard volt- age outputs may be used to transpose a sequence from one note to another without affecting the pitches produced by the

15、other voltage in controlling the other voice module. 3. The SEQUENCE LENGTH switch is used to shorten a full eight- step sequence down to anywhere from seven steps to only one. When this switch, for example, is set to 7, the sequencer will count through positions 1-7 and then skip the 8th step, star

16、ting over instead from position 1. This is useful in set- ting odd or asymmetrical rhythms. 4. The two rotary pots in this section of the panel determine respectively the RANGE covered by the sample/hold output vol- tage, and the amount of LAG (low-frequency filtering) applied to the sample/hold vol

17、tage. Turning the lag control to the right produces, in other words, the same effect on pitches being governed by the sample/hold, that the PORTAMENTO control produces on pitches being governed by the keyboard. 5. This is the MASTER CLOCK that steps the sequencer and oper- ates the sample/hold. The

18、rotary knob determines the frequency of this clock-i.e. the stepping rate or tempo. The three-posi- tion switch turns the clock on and off; it can also be clicked momentarily down to advance the sequencer one step or to cause a new sample voltage to be taken. A switch is incorporated into the clock

19、tempo control, allowing the knob to be pulled out from the panel. In this position, the clock rate will be controlled by SEQUENCER OUTPUT TWO. This voltage control of the clock frequency is also affected by the third VOLTAGE ASSIGNMENT SWITCH: in its uppermost position (#2 above), the keyboard volta

20、ge is added to sequencer output two and will therefore also determine the clock rate. 5 THE VOICE MODULES The panel controls on each module are identical. In the diagram above they are grouped by similar functions for easy under- standing. The asterisks in sections la, 2a, 3, 4, 7, 8, and 10 are for

21、 use in the following section of the manual. la, 2a. These are the MANUAL TUNING CONTROLS for VCO 1 and VCO 2 respectively. The lower flanged portion of each knob is for coarse tuning, and the upper part of the knob is a vernier fine tuner. lb, 2b. The three-position switch selects one of three cont

22、rol signals, indicated on the panel, to be routed through the rotary pot just above the switch. If this knob is rotated to the right, the selected control voltage will affect the VCO pulse width. If this knob is rotated to the left, the selected control voltage will affect the VCO frequency. If the

23、knob is left in its vertical position (as in the photograph), the selected control voltage will have no effect on the VCO at all. 1c, 2c. These are MANUAL PULSE WIDTH CONTROLS for the two oscillators. At vertical, as in the diagram, the pulse produced in each cycle is exactly one-half as long as the

24、 cycle itself; 6 such a signal is called a square wave. As the knob is rotated in either direction from vertical, the pulse becomes wider (to the right) or narrower (left). 3. When this switch is moved to the right, VCO 2 is SYNCHRO- NIZED to the frequency of VCO 1. VCO 1 is not affected by this swi

25、tch regardless; but VCO 2, when it is syncd to VCO 1, can produce only harmonics of the frequency to which VCO 1 is set. When the switch is off the two oscillators are completely inde- pendent. 4. These are the three MANUAL CONTROLS for the filter. The smaller knob at the lower right determines whet

26、her the filter will act as a bandpass filter (at the click-stop position labelled BP ), lowpass filter (immediately clockwise from the click-stop, labelled LP), notch filter (vertical, at the word notch), or highpass filter (extreme clockwise, labelled HP). Do not try to turn the knob clockwise past

27、 the highpass stop. The large vernier control at the upper left determines the fre- quency at which the filter begins to take effect, or the center frequency of the bandpass and notch modes. In the low- and high- pass modes the frequency at which the filter begins to have some effect on a signal pas

28、sing through it is called the cutoff frequency of the filter. The large single knob labelled RESONANCE determines the filter resonance at its cutoff frequency. When this knob is fully counterclockwise the filter resonance is at a minimum; as it is rotated to the right the resonance increases. RESONA

29、NCE is a term for the gain (i.e. roughly, loudness) of the filter at or near its cutoff frequency. At maximum resonance, for example, the filter amplifies strongly any components of the input sig- nal that lie within a semitone or so of the cutoff frequency, but virtually ignores components that are

30、 not near the cutoff frequency. In other words, a pronounced peak occurs in the filter fre- quency response as the resonance is increased, which grows higher in amplitude as it grows narrower in width. When the center of this peak is exactly at the frequency of an audio input to the filter, a relati

31、vely weak signal can drive the filter to produce a quite strong output. 5. The switch selects one of three sources for a control input to the filter. The left and right positions are self-explana- tory; the center position carries a signal from the SAMPLE/HOLD section of the mini-sequencer panel. Th

32、is signal is independent of any of the routing and assignment switches in the 7 mini-sequencer. The knob is a reversible attenuator for the control signal selected; in the photographed position, no sig- nal will pass through to have any effect on the VCF CUTOFF FRE- QUENCY. As the knob is rotated to

33、 the right, the selected control signal affects the VCF directly; as the knob is rotated to the left, the signal affects the VCF inversely , i.e. a posi- tive voltage drives the VCF frequency down rather than up. 6. These are the AUDIO INPUT SELECTOR/ATTENUATORS for the VCF. In the photographed posi

34、tion, they are all OFF. Unless at least one of these is open, i.e. rotated either to left or to right, the module will produce no sound regardless of any of the other settings anywhere on the module panel. The first knob on the left, labelled VCO 1, selects either the sawtooth (leftwards) or pulse (

35、rightwards) signal from VCO 1 as an audio input to the VCF. The second one does the same for signals from VCO 2. The left side of the third knob is not connected to any signal ( except that for the first VOICE MODULE there is a Jack at the back of the synthesizer for an external audio signal input,

36、and this jack is wired to the left position of the knob on module one ); the right side is wired directly to the output of the NOISE GENERATOR that is part of the sample/ hold in the minisequencer. Noise, filtered in various ways, is used in the production of wind, thunder, and motor sounds, as well

37、 as many percussion effects. Signals from the two oscillators and the noise generator may be mixed in various proportions by opening all three of the input attenuators at the same time. 7. These three rotary pots determine the behavior of ENVELOPE GENERATOR ONE. The first two knobs set two time cons

38、tants : the attack time constant is the amount of time required for the ENV 1 OUTPUT VOLTAGE to rise from 0 to maximum, and the decay time constant is the amount of time required for the ENV 1 OUTPUT VOLTAGE to fall. .from maximum to the level set by the third knob, and .from this sustain level back

39、 to 0. The third knob determines, not a time constant , but a voltage constant . This constant is the level at which the ENV I output will be sustained (hence the label) for as long as a GATE sig- nal is present at the gate input of the envelope generator. GATE signals may originate either from the

40、keyboard or from the MASTER CLOCK in the minisequencer. They act as begin-end instructions to the envelope generators; on the appearance of a gate signal at its input, an envelope generator commences an ATTACK-DECAY-SUSTAIN-cycle, and when the gate signal ends, the envelope generator executes a fina

41、l DECAY as described 8 above. Gates are thus members of the general class of TIMING signals; other timing signals are TRIGGERS. The Oberheim 2-voice synthesizer does not use trigger signals. 8. These three knobs set the constants attack time , decay time , and sustain voltage level for ENV 2. NOTE:

42、as you can determine by examining the control voltage select switches for the two VCOs and the VCF, ENV I can be used to control VC0 1, and ENV 2 can be used to control VCO 2 andlor the VCF. in ordinary keyboard use, i.e. without special effects, ENV I will be used only to control the VCA, and ENV 2

43、 will be used only to control the VCF. 9. Each voice module contains a LOW-FREQUENCY OSCILLATOR. The output of this oscillator is a sine wave and is available to control the VCOs and/or the VCF through the voltage select switches described under #lb, 2b, and 5. The actual frequency of the LFO is set

44、 by the knob indicated here. 10. Normally the VCA is controlled by ENV 1 (see NOTE above). In order to simplify the operation of the voice module while learning, or whenever it is necessary to hear continuous sound, this VCA BYPASS SWITCH can be moved to the on (right) position. This disconnects ENV

45、 1 from the VCA control input and leaves the VCA permanently wide open so that signals pass through it completely unaffected; in effect, the VCA is bypassed. Moving the switch to the left closes the VCA again and reinstates the control voltage from ENV 1. 11. This light indicates the presence of a G

46、ATE signal (see #7 above) at the input to the two ENVELOPE GENERATORS. Press a key; depending on the position of the 2ND-VOICE switch at the left of the keyboard, one or both of the indicator lights will go on. NOTE: Even before hearing any sound from the synthesizer, you can use these indicator lig

47、hts to understand the function of the VOLTAGE ASSIGNMENT SWITCHES (minisequencer #2). Move the two left switches up to the SIH position, and press a key or two; note that the lights do not now go on. Start the CLOCK (minisequencer #5) and note that they go on and off regularly at a rate that increas

48、es as the clock frequency increases. 9 FIRST STEPS A. CONTINUOUS SOUND Begin by setting all the controls on VOICE MODULE ONE to the positions indicated in the diagram/photograph on page five, except for #1a, 2a, 3, 4, 7, 8, and 10, which should be set to the positions indicated by the asterisks. Ope

49、n the MASTER OUTPUT LEVEL control to about two-thirds. Open the OUTPUT LEVEL CONTROL for voice module one about two-thirds. Now opening any one or more of the AUDIO INPUT SELECTORS (#6) in voice module one will allow you to hear a signal from the corresponding signal source. Listen to each of the VCO signals, and to the noise generator (the third knob, rotated clockwise from center, brings in the noise generator). Experime